Hi, I work with opencv, and use Slackware64 -current, but now I get this error: opencv.pc not in PKG_CONFIG_PATH.
It's strange because have always work, I check PKG_CONFIG_PATH and get this: /usr/local/lib64/pkgconfig:/usr/lib64/pkgconfig:/usr/local/lib64/pkgconfig
Why /usr/local/lib/pkgconfig desapere?

Thank's, sorry my bad english

Your PKG_CONFIG_PATH env variable is set for a 64-bit environment. /usr/local/lib/pkgconfig is for 32-bit meta-data (*.pc) files.

I don't know whether Slackware64 is multilib or not. Assuming it is, I don't know what the Slackware way for dealing with 32-bit and 64-bit paths is.

You could define two env variables PKG_CONFIG_PATH32="/usr/local/lib/pkgconfig:/usr/lib/pkgconfig" and PKG_CONFIG_PATH64="/usr/local/lib64/pkgconfig:/usr/lib64/pkgconfig". When you build 32-bit packages, set PKG_CONFIG_PATH="${PKG_CONFIG_PATH32}". Use PKG_CONFIG_PATH64 when building 64-bit packages.

In its present state, Slackware64 is not multilib. It appears to be multilib capable in that it has both /usr/lib and /usr/lib64, but /usr/lib is empty.

Well, having lib and lib64 would be the *most* FHS compliant. I wonder whether the toolchain is built multilib or if the intention is to install precompiled 32-bit binaries and libraries? I don't know enough about Slackware to know how much of a PITA it would be for pkgtools to accomodate both ABI. I'd guess not real tough since it's (AFAIK) just shell scripts. The PackManUtil (bunch of shell scripts) I use on my multilib CLFS machines handles both ABI.

This has been the subject of much speculation in the Slackware forum. At the moment, it looks as if Slackware64 is going to be "pure" 64, but since it is likely users will need 32 bit programs, it will be FHS compliant and allow users to add 32 bit libraries as they need. Also, the 32 bit version of Slackware isn't going anywhere, so people can safely stay in the 32 bit world if they need.

I suspect that is isn't that much of a PITA, but more of a philosophical stance. Slamd64 is a 64 bit Slackware derivative that is multilib and I never saw any indication that it was a nightmare to maintain. Patrick Volkerding doesn't seem to have made any statements about pure vs multilib since the introduction of Slackware64, but based on past indications, the situation as it currently exists is likely to be how it stays (at least in my opinion).